Method and apparatus for mixing and dispensing

ABSTRACT

Method and apparatus for the mixing and dispensing of a multiple component material composition wherein said component materials are supplied substantially continuously in controlled ratio in a substantially concurrent mixing and dispensing cycle, and said cycle is repeatable to form successive mixing and dispensing as required in processes such as mold filling.

United States Patent, [191 Simmonds, Jr.

[ METHOD AND APPARATUS FOR MIXING AND DISPENSING 75 Inventor: Robert c.Simmonds, Jr., Topsfield,

Mass.

[73] Assignee: USM Corporation, Boston, Mass. Y

[22] Filed: Oct. 13, 1972 [21] App]. No.: 297,382

52 U.S.Cl. 259/7,23/25 2R [51 Int. Cl. B28c 7/04 [58] Field of Search259/7, 8, 9, 10, 154, 148, 259/149, 164, 165, 161, 162; 222/70, 134,

[ 56] References Cited UNITED STATES PATENTS 3,123,342 3/1964 Little259/7 [451 Feb. 26, 1974 3,409,174 11/1968 Radcliffe 222/70 3,448,9676/1969 Seanor'. 259/154 3,608,869 9/1971 Woodle 259/7 3,632,022

1/1972 Simmonds 222/134 Primary Exam inerR 0bcrt W. Jenkins Attorney,Agent, or Fir'm- -Vincent A. White; Richard B. Megley; Howard R.Berkenstock, Jr.

[ 5 7 ABSTRACT Method and apparatus for the mixing and dispensing of amultiple component material composition wherein said component materialsare supplied substantially continuously in controlled ratio in asubstantially concurrent mixing and dispensing cycle, and said cycle isrepeatable to form successive mixing and dispensing as required inprocesses such as mold filling.

16 Claims, 8 Drawing Figures mimznrzazs 1974 SHEET 1 OF 2 w w w METHODAND APPARATUS FOR MIXING AND DISPENSING BACKGROUND OF THE INVENTIONmentsubsequently disclosed, the basic liquid ingredients, when combined,form a reactive mixture which still may be in a controlled reactingcondition when dispensed from the mixer.

Prior art devices for mixing and dispensing utilized in applicationsanalogous to the present invention generally have operated on a batchmixing principle. Illustrative of such devices and applications are: US.Pat. Nos. 3,409,174; 3,632,022; and 3,642,175; all assigned to theassignee of the present invention. These illustrative devices aregenerally for use in mixing and dispensing a polyurethane composition,and in the utilization of which the component ingredients including apolyhydroxyl composition and an isocyanate composition are sequentiallyfed to a mixing chamber in a desired ratio. These prior art devices alsoinclude means whereby the ratio at which the compositions are fed tothemixing chamber may be varied, and means whereby the total quantity ofthe constituent compositions fed to the mix- SUMMARY OF THE INVENTIONThis invention relates to method and apparatus for mixing and dispensinga multicomponent liquid mixture. In accordance with certain features ofthe invention there are provided method and apparatus for performing theoperative steps of supplying a first component ingredient to a mixingchamber and metering same, supplying a second component ingredient tothe mixing chamber, and metering same, substantially con-v currentlywith the first ingredient, measuring the relaing chamber may be varied.(including means for accordingly varying the volume of the mixingchamber.)

One of the problems existing with the prior art, batch type devices hasbeen their volumetric limitations. Specifically in applications of themixing devices for supplying plastics molding equipment, the size of amolded part was limited by the technology limiting mixer volume. Thereaction characteristics ofmixed quantities of reacting componentmaterialstended to vary when chamber volumes were increased beyond'knownsizes. Further, larger batches required longer times to fill theincreased size mixing chambers as well as increased the specific timesrequired for proper mixing of component ingredients. Such increased timefactors interjected mixed material history variations which disruptedestablished injection history requirements.

, The present development provides a method and apparatus for mixing anddispensing material wherein constituent ingredients are fedsubstantially contempowithout previously known volumetric limitations.

While the illustrative embodimentshows two components being mixed anddispensed the method and apparatus are not to be considered-so limited.Clearly any number of component ingredients may be accommodated, beingcombined in desired relative proportions.

tive proportion of the component ingredients being supplied to thechamber, comparing the measured ratio to a predetermined standard ratio,controlling the metering of one of the component ingredients so as tomaintain the ratio at the predetermined standard, mixing the ingredientssupplied the chamber substantially concurrently with the supply theretoand dispensing the mixed ingredients from the chamber substantiallyconcurrently with the continuing supplying of the ingredients to thechamber.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates in block diagram formtypical apparatus for performing the novel mixing and dispensing ofcomponent materials forming a reactive mixture.

FIGS. 2-8 illustrate the operative sequence of an embodiment of thedisclosed novel method and apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT The illustrative apparatusisadapted for use in dispensing a multiple component material such as apolyurethanecomposition. Reference number 10 indicates a mixing chamberpreferably having a variable volume. Chamber 10 includes cylinder 12having a piston 14 slidably disposed therein and connected to a pistonrod 16. Piston 14 while slidably disposed in cylinder 12 is closelyreceived therein so as to prevent the undesired escape of materialsbeing mixed therefrom.

Piston rod 16 is connected to actuator means 18 for driving piston 14,and controlling the volume of chamber 10. Position sensing means such asa position transducer 17 may be operably connected to piston 14 as bybeing drivenby rod 16, to sense the position of piston 14 with cylinder12. Actuator 18 may include hydraulic or electrical motor means forpositioning rod 16 and piston "14. Actuator 18 as well as transducer 17are operably connected to master control means 20, as indicated in blockform. Master control 20 for the illustrative polyurethane mixingisdivisable into three basic control functionsas indicated; being mixerLogic section, a first component control section and a secondpolyisocyanate component control section.

Extending into cylinder 12'are first and second inlet ports, 22 and 24,respectively. Preferably, valving means 23 and 25 are disposed withinports 22,24 to se-.

quential, batch-type variable volume mixing chambers and associatedhardware for the molding of polyurethane material.

lnlet ports 22 and 24 are connected through conduit means 42 and 44respectively to first and second component metering means 46 and 48respectively. It is to be understood that a variety of means such ascontinuous or intermittent pumps could be used to supply ingredientsfrom bulk supplies as a means. However, for illustrative purposesmetering means 46 and 48 may be cylinders 50 and 52 having meteringpistons 54 and 56 may supply mold 34 with a shot of polyurethane formingmaterial, then rest until a subsequent molding operclosely received butslidably disposed therein. Metering I pistons 54 and 56 may be motivatedby rod means 58 and 60 through actuator means 62 and 64. In theillustrated embodiment, metering cylinder 50 may supply the polyhydroxylcomponent of the polyurethane compound to be formed in chamberandcylinder 52 may supply the isocyanate component. Component meteringmeans 46 and 48 include sensing means capable of generating a controlsignal directly related to metered component delivered to mixing chamber10. In the in,- stance of the illustrated metering cylinders 50 and 52,position transducers 66 and 68 on polyhydroxyl and isocyanate pistonrods'58 and .60 respectively, supply an indicationof piston 54, 56location and thus, of the rate or volume component material supplied byeach of the means 46,48. Actuator means 62 and 64 may conveniently behydraulicly or electrically powered devices such ashydraulic orelectrical motors (rotary or reciprocating), controllable through amaster control means as indicated in FIG. 1. A wide variety of controlmeans are commercially available and known'to those skilled in the artwhich may be selected and combined in accordance with the invention toprovide the function subsequently described.

Master control means 20 maybe functionally divided into logic section 20which orders and controls the sequence of function of the illustratedmixing and dispensing apparatus, and metering control section 20".Metering control section 20'-' serves to direct the operation ofmetering 'means 46,48 through actuators 62,64. Thus section 20 isdivided into first component (polyhydroxyl) control section 21' andsecond component (polyisocyanate) control section 21".

Master control 20 maybe programmed for the illustrative apparatusmechanically, electrically and/or hy-, draulicly to cause thepolyhydroxyl component and isocyanate component to be metered fromcylinders 50,52 through conduits 42,44, valves 23,25, inlet ports 22,24into mixing chamber 10. Ratio control means 70 functions to instructcontrol 20 of the preselected relative proportion of the componentmaterials to be supplied and to maintain the proper ratio of componentsduring the mixing and dispensing cycle. The elements and function ofmeans 70 to perform this proportioning will be described in detailsubsequently.

ation is ready to be performed. During such rest period, the filled moldmight be opened, emptied and prepared for a subsequent shot immediatelyor, the molding machine might be equipped with a plurality of moldstations, and a prepared station cycled into operative engagement withthe mixing chamber. U.S. Pat. No. 3,632,022 is illustrative of suchapparatus. It is also possible to use the apparatus in an extendedoperating cycle such as for the extrusion of a mixed material.

During the sequential operation of chamber 10 to fill subsequent moldswith a polyurethane forming composition the chamber starts from a restcondition. In normal operating sequence, chamber 10 in the restcondition contains a residuum of material being the remnants(subsequently described) of a previous mixing cycle. This condition isillustrated in FIG. 2, showing the chamber 10, valves 23, 25 and 28 inthe closed condition and the piston 14in a position providing a volumeto accommodate the residuum of material Q. In the illustrated apparatusthis residuum Q may be rich in polyhydroxyl component ingredient.

When a mold 34 is ready for a shot, actuator 40 signals control 20 ofthe mold s readiness. Control 20-then opens valve 25 and actuatesmetering means 48 through control 21" and actuator 64 to supply aquantity of isocyanate componentingredient through conduit 44 and port24 to cylinder 12. This component is supplied in a quantity calculatedto bring the' polyhydroxyl rich residuum back to the relative proportionfor controlled reaction. This sequence is illustrated in FIG. 3.Concurrent with the addition of polyisocyanate component ingredient,control 20enables chamber 10, to increase its volume by raising piston14, as by signaling actuator 18 and moving rod 16 or by allowing theincoming material to force piston 14 upward. Transducer l7 signals thetravel of piston rod 16 and control 20 in-- terrupts the actuation ofactuators 18. and 64 when the mixture in cylinder 12 is returned to aproperly proportioned mixture. I 1

Control 20 then actuates ratio control means '70 which signalsconcurrent supply of component ingredients to chamber 10. Control means21' and 21" initiate the metering of components from means 46,48 throughconduits 42,44 and ports 22 and 24 respectively. Control 20 hasconcurrently opened valves 23 and 25 (25 may already be open from theprevious step) and coordinately increases the value of chamber 10accommodate the increasing volume of the mix (output valve 28 remainingclosed). This event is illustrated at FIG. 4. Ratio control means 70,from the moment of actuation by control 20 receives the quantityinformation of component ingredientsmetered as measured by transducers66,68 and computes ratio information which is supplied to controls 21,21 These controls cause the metering means 46,48 to bring the mixture onratio" (if not at the preselected value) and supplies a signal tocontrol 20 when this condition is reached (zero error indication). In.practice, the mixture may be brought on ratio by return ofpolyisocyanate in the previous step and no additional metering in thisstep may be necessary.

Once control 20 receives the on, ratio or zero error indication, themixture in chamber 10 is ready to begin being dispensed into mold cavity38, FIG. 5 illustrates this event in the mixing and dispensing sequenceof the present invention. Valve 28.is opened by control and thereacting, polyurethane forming mixture is injected into cavity 38.Metering means 46,48 continue to supply component ingredients, at properratio as controlled by'means 70, through control 20' and actuators62,64. Control 20 adjusts the volume of cylinder 12 to an optimum mixingvolume for the concurrent mixing and dispensing of material Q. (FIG. 6)

Volume control means 72 monitors the amount of component materialssuppliedto cylinder 12 in the illustrated embodiment by observing themovement of pistons 54,56 (by rods 58,60 and transducers 66,68). Thecomputed total quantity of component ingredients supplied is compared toa preselected total quantity (shot size) and when this value is reached,the master control 20 observes the event. Master control 20 may thensignal shutoff of component materials (as by closing valves 23,25 andterminating the metering'of components by means 46,48).

In the preferred embodiment, control 20 anticipates the completion ofthe supply of material to mold cavity 38 approaching the conclusion ofthe dispensing cycle. Control means causes the volume of material stillremaining within cylinder 12 to be reduced to a predetermined nominallevel, insofar as is-practical, to evacuate the cylinder 12 of thereacting, mixing polyurethane forming components. Control 20, throughactuator 18 causes the advance of piston 14 toward outlet port 26. Oncepiston 14 has bottomed out (reached the predetermined advanced positionindicated by dotted'lines 14') the dispensing or injection into mold 3,6is complete. Valve 28 is ordered closed. This conditionis illustrated in-FIG. 7.

' Since there is a residuum of reacting polyurethane forming materialremaining within chamber 10, control 20 is programmed to dilute theresiduum mixture to quench the polyurethane forming reaction. In theillustrated embodiment, at the completion of injection, a predeterminedquantity of polyhydroxyl component is supplied by metering means 46through opened valve .23 and port 22. Concurrently control 20 increasesthe volume of cylinder 12 to. accommodate the dilution of the residuum;See FIG. 8.-

It should be noted that the above disclosed method of mixing anddispensing and the apparatus therefor describe a sequence of-functionnot previously performed in the related mixing and dispensing arts. Itis to be further appreciated that the disclosed concurrent filling ofthe mixing chamber and dispensing of mixed material is volume limitedonly the size of the component metering means (46,48). Previousbatch-type mixing/dispensing systems have been limited by the volume ofthe mixingchamber, and/or the; prior practice of sequentially fillingthe mixing chamber .with the components of the reacting mixture.

, Further contributing to the success of the present method andapparatus for mixing is the method and apparatus for controlling theratio-of component materials achieved by ratio control means 70. Ratiocontrol 70 is conveniently illustrated in elemental electricalblock-diagram form, however it should be understood that known fluidicor mechanical equivalents of the combined elements could be used.

Transducing means 66 and 68 provide quantitative information of themetered components supplied by means 46,48 to mixing chamber 10,; beingconveniently ming means 74 which in turn, generates an error signalvproportional to the difference of the quantitative signals. In theillustrated embodiment, summing means is illustrated as including aratio signal input 76 by which one of the other incoming quantitativesignals may be modified with the information as to preferred relativeproportion of ingredients. Thus the output of means 74 may reflect theerror from the desired ratio valve. Ratio signal input 76 could berendered unnecessary in those situations where metering means 46,48 hada geometrical relationship which provided the desired ratio in theirbasic function (as by causing cylinders 50,52 to be of comparativediameters equal to the desired ratio),

The output signal of means 74 (ratio error) is conveniently supplied toindicator means 78, a zero error detector 80 and a ratio drive control82. Zero error detector 80 monitors the error signal output from means74 and provides an output onratio signal to the master control 20 whenthe ratio error is within the zero. limits of detector 82. Mastercontrol 20, upon receipt of on ratio information may appropriatelysignal concurrent mixing and dispensing of the reacting polyurethaneforming mixture. 1

The significance of"on ratio signaling may be appreciated by furtherreference to the previously described dilute shot which quenches thereaction in the residuum of material at the end of a mixing/moldingcycle. For, until the polyhydroxyl component rich charge within chamber10 at the beginning of a subsequent cycle is brought up to the desiredratio, a moldready mixture is not available in chamber 10 for injection(dispensing through outlet 28). Thus, in the polyhydroxyl rich stage, atthe beginning of a cycle, master control 20 disenables the actuation offurther'polyhydroxyl metering, until the polyisocyanate component levelin chamber reaches the on ratio" value. At this time in the cycle, thefirst component metering means 46 may be actuated to follow the ratio.

there were no other system upsets to disturb the individual meteringfeed rates. However, ratio drive control 82 receives the ratio ratesignal from means 84 as a bias" signal ad the error signal from themeans 74. Ratio drive control 82 then produces a modified drive signalreflecting the required ratio error correction which may then bedirectly supplied to metering actuator 62 (such as through control 21"for. proper overall control coordination). Small errors in ratio may bedetected and corrections superimposed upon the drive rate signalsupplied from means 84. Thus, the signal which is alternately suppliedto actuator 62 to correct ratio, may be the sum of inputs to drivecontrol 82, and of high accuracy when compared to a system which wouldgenerate an analogy drive rate signal based on error observation.

The method and apparatus of the present invention have been heredisclosed in-basic form, as particularly adapted to the molding ofpolyurethane compound formed from polyhydroxyl and polyisocyanatecomponent ingredients. Other fields of application of the instant methodand apparatus, or modification thereof are in the application ofcoatings for sealing, adhering, protecting or decorating applications,the manufacture of laminations, 'or thermosetting extrusions, or thelike. It then will be apparent that many variations may be made in thedisclosed method and apparatus to accommodate a particular need withoutfrom the spirit and scope of the invention as defined in the followingclaims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A method of mixing and dispensing a multieomponent material whereinthe component ingredients are supplied in measured relative proportionsto a mixing chamber, comprising the steps of: metering a first componentingredient to said mixing chamber; metering a second componentingredient to said mixing chamber,

v substantially concurrently with said first ingredient;

measuring the relative proportion of said ingredients being supplied tosaid chamber; comparing said relative proportions of said components toa predetermined standard; controlling said metering of a componentingredient so as to maintain said relative proportions at saidpredetermined standard; 'mixing said ingredients substantiallyconcurrently with'the metering of said ingredients to said mixingchamber; dispensing said mixed ingredients from said chambersubstantially concurrently with said metering said component ingredientswhile said relative proportion is at said predetermined standard.

2. A method according to claim 1 wherein said mixed materials arereaction producing and are intermittently dispensed in measured quantityto a receptacle such as a mold wherein the operative mixing anddispensing steps include diluting said relative proportion of theresiduum said constituent ingredients in said mixing chamber subsequentto the dispensing of said measured quantity to said receptacle with apredetermined quantity of an ingredient, thereby quenching the reactionof said mixed materials in said chamber by substantially changing therelative proportion of said component ingredients Wm H '3. A methodaccording to claim 2 wherein said mixing chamber contains theingredients of said quenched reaction and including the step ofreturning said quenched reaction to the predetermined relativeproportion of reactive ingredients by supplying a predetermined quantityof the other of said component ingredients of said reaction producingmixture, prior to said'supplying of component ingredients for concurrentmixing and dispensing.

4. A method according to claim 3 including the step of decreasing thevolume of 'said mixing chamber to a predetermined minimum valueimmediately prior to completion of filling said receptacle andsubsequently increasing said mixing chamber volume subsequent to saiddispensing and concurrently with said supplying of said dilutingcomponent ingredient.

5. A method according to claim 3 includingthe step of increasing thevolume of said mixing chamber concurrently with the metering of saidother component ingredients during the reestablishing of saidpredetermined component ingredient relative proportions and reactingthereof.

6. A method according to claim 1 including the steps of varying thevolume of said mixing chamber being supplied with said metered componentingredients by increasing said chamber volume during the steps ofmeasuring, and comparing said relative proportions and controlling saidmetered rate to obtain said predetermined standard.

7. A method according to claim 6 including the step of varying thevolume of said mixing chamber to a predetermined volume concurrentlywith said dispensing whereby said chamber volume, during the. mixing anddispensing step will be at a volume wherein optimum mixing may beachieved.

8. Apparatus for dispensing a multicomponent composition provided by themixing together of at least two component ingredients comprising: amixing chamber; means for supplying a first component ingredient to saidchamber; means for supplying a second component ingredient to saidchamber; means for metering the first component supplied said chamber;means for metering the second component supplied said chamber; means forcomparing the measurements of said first and second metering means;means for controlling at least one of said supply means to cause saidproportions of said measured supply to meet a predetermined standard;means 'for dispensing said composition;

means responsive to said comparison means to cause said composition tobe dispensed when said predetermined standard is met.

9. Apparatus according to claim 8 including means for varying the volumeof said mixing chamber and means controlling said varying means to causesaid chamber volume to correspond to the volume of components added tosaid chamber.

10. Apparatus according to claim 9 whereincsaid means controlling saidchamber volume is responsive to said comparison means to cause saidvolume to vary to a predetermined mixing standard during said dispensingof said composition. I

11. Apparatus according to claim 9 including means to control saidsupply means to dispense a predetermined quantity of multieomponentcomposition.

12. Apparatus according to claim 11 wherein said means to control saidchamber volume is responsive. to said means to control said quantity ofcomposition to cause said chamber volume to reach a predeterminedminimum volume when said predetermined quantity of composition has beendispensed.

13. Apparatus according to claim 8 including means to inactivate saiddispensing means, means to inactivate said means controlling one ofvsaid supply means to cause said comparison means to meet a predeterminedstandard; and means to supply a predetermined quantity of one of saidingredients to said mixing chamber subsequent to inactivation of saidabove named means, whereby at the end of dispensing, the compositionremaining in said chamber is diluted with one of said componentingredients. v

14. Apparatus according to claim 13 adapted to restore said dilutedcomposition remaining in said chamber to a ratio of components to meetpredetermined standard prior to further mixing and dispensing includingmeans to inactivate the supply means of said dilute component, means tosupplya predetermined quantity of the other of said componentingredients to said chamber to cause said proportions of said measuredsupply to said chamber to meet said predetermined standard and means toreactivate said inactivated supply and comparison means.

15. Apparatus according to claim 8 wherein said means for metering saidfirst component ingredient includes means for generating-a signaldirectly proportional to said first metered supply; said means formetering said second component ingredient includes means for generatinga signal directly proportional to said second metered supply; said meansfor comparing said measurements of said metering means include means forcomparing said signals and generating a signal directly proportional tothe difference of said first and second supply signals; said means forsupplying ing said component ingredients substantially concurproportionis at said predetermined proportion; a secsaid first componentingredient to said chamber includes means for supplying said componentat-a predetermined rate; said means for controlling at least one of saidsupply means-to cause said proportions of said measured supply to meet apredetermined standard include said control means adapted to beresponsive to a driving signal being the sum of said signal proportionalto the difference of said first and second supply signals and a signaldirectly proportional to a constant value which would otherwise causesaid controllable supply to bemetered at a rate predetermined to meetsaid predetermined standard. l

.16. A methodof mixing and dispensingsuccessive shots of amulti-component material wherein the com-,

ponent ingredients aresupplied in measured relative proportions to amixing chamber. comprising: afirst stage of substantially continuouslymetering a first component ingredient to'said mixing chamber;substantially continuously metering a second component ingredient tosaid mixing chamber in predetermined relative proportion to said firstcomponent ingredient; mixrently with the metering of said ingredients tosaid mixing chamber, dispensing said mixing ingredients from saidchamber substantially concurrently with said metering of said componentingredients while said relative ingredient in the mixture in said mixingchamber and concurrently increasing the volume of said mixing chamber toaccept said amount of said one component; and a fourth stage of-meteringandtmixing a quantity of saidother component ingredient to bring therelative proportion of said first and second component ingredients' inthe mixture in said chamber to said predetermined standard and,concurrently increasing the volume of said mixing chamber to accept saidquantity of said other component ingredient prior. to repeating thestages of the process. 7 j t

1. A method of mixing and dispensing a multicomponent material whereinthe component ingredients are supplied in measured relative proportionsto a mixing chamber, comprising the steps of: metering a first componentingredient to said mixing chamber; metering a second componentingredient to said mixing chamber, substantially concurrently with saidfirst ingredient; measuring the relative proportion of said ingredientsbeing supplied to said chamber; comparing said relative proportions ofsaid components to a predetermined standard; controlling said meteringof a component ingredient so as to maintain said relative proportions atsaid predetermined standard; mixing said ingredients substantiallyconcurrently with the metering of said ingredients to said mixingchamber; dispensing said mixed ingredients from said chambersubstantially concurrently with said metering said component ingredientswhile said relative proportion is at said predetermined standard.
 2. Amethod according to claim 1 wherein said mixed materials are reactionproducing and are intermittently dispensed in measured quantity to areceptacle such as a mold wherein the operative mixing and dispensingsteps include diluting said relative proportion of the residuum saidconstituent ingredients in said mixing chamber subsequent to thedispensing of said measured quantity to said receptacle with apredetermined quantity of an ingredient, thereby quenching the reactionof said mixed materials in said chamber by substantially changing therelative proportion of said component ingredients.
 3. A METHOD accordingto claim 2 wherein said mixing chamber contains the ingredients of saidquenched reaction and including the step of returning said quenchedreaction to the predetermined relative proportion of reactiveingredients by supplying a predetermined quantity of the other of saidcomponent inGredients of said reaction producing mixture, prior to saidsupplying of component ingredients for concurrent mixing and dispensing.4. A method according to claim 3 including the step of decreasing thevolume of said mixing chamber to a predetermined minimum valueimmediately prior to completion of filling said receptacle andsubsequently increasing said mixing chamber volume subsequent to saiddispensing and concurrently with said supplying of said dilutingcomponent ingredient.
 5. A method according to claim 3 includingthe stepof increasing the volume of said mixing chamber concurrently with themetering of said other component ingredients during the reestablishingof said predetermined component ingredient relative proportions andreacting thereof.
 6. A method according to claim 1 including the stepsof varying the volume of said mixing chamber being supplied with saidmetered component ingredients by increasing said chamber volume duringthe steps of measuring, and comparing said relative proportions andcontrolling said metered rate to obtain said predetermined standard. 7.A method according to claim 6 including the step of varying the volumeof said mixing chamber to a predetermined volume concurrently with saiddispensing whereby said chamber volume, during the mixing and dispensingstep will be at a volume wherein optimum mixing may be achieved. 8.Apparatus for dispensing a multicomponent composition provided by themixing together of at least two component ingredients comprising: amixing chamber; means for supplying a first component ingredient to saidchamber; means for supplying a second component ingredient to saidchamber; means for metering the first component supplied said chamber;means for metering the second component supplied said chamber; means forcomparing the measurements of said first and second metering means;means for controlling at least one of said supply means to cause saidproportions of said measured supply to meet a predetermined standard;means for dispensing said composition; means responsive to saidcomparison means to cause said composition to be dispensed when saidpredetermined standard is met.
 9. Apparatus according to claim 8including means for varying the volume of said mixing chamber and meanscontrolling said varying means to cause said chamber volume tocorrespond to the volume of components added to said chamber. 10.Apparatus according to claim 9 wherein said means controlling saidchamber volume is responsive to said comparison means to cause saidvolume to vary to a predetermined mixing standard during said dispensingof said composition.
 11. Apparatus according to claim 9 including meansto control said supply means to dispense a predetermined quantity ofmulticomponent composition.
 12. Apparatus according to claim 11 whereinsaid means to control said chamber volume is responsive to said means tocontrol said quantity of composition to cause said chamber volume toreach a predetermined minimum volume when said predetermined quantity ofcomposition has been dispensed.
 13. Apparatus according to claim 8including means to inactivate said dispensing means, means to inactivatesaid means controlling one of said supply means to cause said comparisonmeans to meet a predetermined standard; and means to supply apredetermined quantity of one of said ingredients to said mixing chambersubsequent to inactivation of said above named means, whereby at the endof dispensing, the composition remaining in said chamber is diluted withone of said component ingredients.
 14. Apparatus according to claim 13adapted to restore said diluted composition remaining in said chamber toa ratio of components to meet predetermined standard prior to furthermixing and dispensing including means to inactivate the supply means ofsaid dilute component, means to supply a predetermined quantity of theother of said component ingredients to said chamber to cause saidproportions of said measured supply to said cHamber to meet saidpredetermined standard and means to reactivate said inactivated supplyand comparison means.
 15. Apparatus according to claim 8 wherein saidmeans for metering said first component ingredient includes means forgenerating a signal directly proportional to said first metered supply;said means for metering said second component ingredient includes meansfor generating a signal directly proportional to said second meteredsupply; said means for comparing said measurements of said meteringmeans include means for comparing said signals and generating a signaldirectly proportional to the difference of said first and second supplysignals; said means for supplying said first component ingredient tosaid chamber includes means for supplying said component at apredetermined rate; said means for controlling at least one of saidsupply means to cause said proportions of said measured supply to meet apredetermined standard include said control means adapted to beresponsive to a driving signal being the sum of said signal proportionalto the difference of said first and second supply signals and a signaldirectly proportional to a constant value which would otherwise causesaid controllable supply to be metered at a rate predetermined to meetsaid predetermined standard.
 16. A method of mixing and dispensingsuccessive shots of a multi-component material wherein the componentingredients are supplied in measured relative proportions to a mixingchamber comprising: a first stage of substantially continuously meteringa first component ingredient to said mixing chamber; substantiallycontinuously metering a second component ingredient to said mixingchamber in predetermined relative proportion to said first componentingredient; mixing said component ingredients substantially concurrentlywith the metering of said ingredients to said mixing chamber, dispensingsaid mixing ingredients from said chamber substantially concurrentlywith said metering of said component ingredients while said relativeproportion is at said predetermined proportion; a second stage ofsubstantially concurrently cutting off entry of said first and secondcomponent ingredients and reducing the volume of said chamber to expel amajor portion of said mixed ingredients from said chamber; a third stageof cutting off discharge of mixed ingredients from said chamber;metering a predetermined amount of one of said component ingredientsinto said chamber and mixing it with mixed components remaining in saidchamber to dilute the relative proportion of the other ingredient in themixture in said mixing chamber and concurrently increasing the volume ofsaid mixing chamber to accept said amount of said one component; and afourth stage of metering and mixing a quantity of said other componentingredient to bring the relative proportion of said first and secondcomponent ingredients in the mixture in said chamber to saidpredetermined standard and concurrently increasing the volume of saidmixing chamber to accept said quantity of said other componentingredient prior to repeating the stages of the process.